Various active implantable devices are available or in development for treating and/or diagnosing numerous ailments. Some examples include cardiac assist devices, pacemakers, defibrillators, cardiac monitors, neurostimulation and neuromodulation systems, drug and medication pumps, and others. A patient may have multiple implanted devices and may benefit in some circumstances by enabling such devices to communicate with one another. Because these implantable devices are generally reliant on battery power, communication between devices should be designed for efficiency and to limit power consumption.